Laminated glass article with aperture formed therein and methods for forming the same

Abstract

A glass article (100) includes a core layer (102) formed from a core glass composition with a core coefficient of thermal expansion (CTE) and first (104) and second (106) cladding layers fused to first and second major surfaces of the core layer (102) and formed from a clad glass composition comprising a clad CTE. An aperture (120) extends through each of the core layer (102), the first cladding layer (104), and the second cladding layer (106). The clad CTE is less than the core CTE such that each of the first (104) and second (106) cladding layers is under a compressive stress and the core layer (102) is under a tensile stress. A flexural strength of the glass article (100) can be at least about 75 MPa. A peak load sustainable by the glass article (100) in a modified ring-on-ring test can be at most 96.5% less than a peak load sustainable by a reference glass article in the modified ring-on-ring test.

What is claimed is: 
     
       1. A method for forming an aperture in a laminated glass article, the method comprising:
 forming a pilot hole through the laminated glass article with a piercing tool having an ADG parameter of less than or equal to 12% as determined by the equation, 
 
       
         
           
             
               ADG 
               = 
               
                 
                   
                     1 
                     ⁢ 
                     0 
                     ⁢ 
                     α 
                     ⁢ 
                     
                       D 
                       η 
                     
                   
                   ρ 
                 
                 * 
                 1 
                 ⁢ 
                 00 
                 ⁢ 
                 % 
               
             
           
         
       
       where D η  (mm) is a tip diameter of the piercing tool, α is an included angle of a tip of the piercing tool such that the tip is tapered, and ρ is an average grit size (ANSI) of abrasive material on the piercing tool, the laminated glass article comprising a core layer disposed between a first glass cladding layer and a second glass cladding layer, the core layer comprising a core glass composition comprising a core coefficient of thermal expansion (CTE), each of the first glass cladding layer and the second glass cladding layer comprising a clad glass composition comprising a clad CTE, the clad CTE less than the core CTE such that each of the first glass cladding layer and the second glass cladding layer is under a compressive stress and the core layer is under a tensile stress; and
 enlarging the pilot hole formed through the laminated glass article with a shaping tool to form the aperture. 
 
     
     
       2. The method of  claim 1 , wherein the piercing tool comprises an included angle of less than about 15°. 
     
     
       3. The method of  claim 1 , wherein the piercing tool comprises a tip diameter of less than about 0.5 mm. 
     
     
       4. The method of  claim 1 , wherein the piercing tool comprises abrasive particles of 400 grit or finer disposed on an outer surface of the piercing tool. 
     
     
       5. The method of  claim 1 , wherein the piercing tool penetrates through a thickness of the laminated glass article by a predetermined depth from about 105% to about 115% of the thickness of the laminated glass article. 
     
     
       6. The method of  claim 1 , wherein enlarging the pilot hole with the shaping tool is performed within at least a minute of forming the pilot hole with the piercing tool. 
     
     
       7. The method of  claim 1 , wherein forming the pilot hole through the laminated glass article comprises rotating the piercing tool about a piercing tool axis at a rotational speed of at least about 50,000 rpm. 
     
     
       8. The method of  claim 7 , wherein forming the pilot hole through the laminated glass article comprises advancing the piercing tool through the laminated glass article at a speed from about 10 mm/min to about 15 mm/min. 
     
     
       9. The method of  claim 1 , wherein enlarging the pilot hole comprises translating the shaping tool within the laminated glass article. 
     
     
       10. The method of  claim 1 , further comprising flowing coolant from about 1300 ml/min to about 1700 ml/min to cool at least one of the piercing tool and the shaping tool. 
     
     
       11. The method of  claim 1 , wherein the shaping tool comprises abrasive particles disposed on an outer surface of the shaping tool. 
     
     
       12. The method of  claim 11 , wherein the shaping tool is a first shaping tool comprising a first grit finish and the method further comprises:
 inserting a second shaping tool comprising a second grit finish that is finer than the first grit finish into the aperture after enlarging the pilot hole with the first shaping tool. 
 
     
     
       13. The method of  claim 12 , wherein the first grit finish of the first shaping tool is about 400 grit or finer and the second grit finish of the second shaping tool is about 800 grit or finer. 
     
     
       14. The method of  claim 1 , further comprising subjecting the laminated glass article to an ion exchange process after formation of the aperture.